Method of producing liquid polymeric chlorotrifluoroethylene



Patented July 8, 1952,

METHOD OF PRODUCING LIQUID POLY- MERIC CHLOROTRIFLUOROETHYLENE John J. Padbury, Stamford, and Edward L. Kropa, Old Greenwich, Conn., assignors to American Cyanamid Company,

New York,

N. Y., a corporation of Maine No Drawing. Application March 31, 1949, Serial No. 84,727

'2 Claims. (-01. 260-653) This invention relates to an improved method of producing liquid polymeric chlorotrifluoroethylene, and is especially concerned with such a method which comprises contacting monomeric. chlorotrifluoroethylene in the vapor phase and at a temperature within the range of 150 C. to 460 C., preferably from about 200 C. to about 400 C., with an alcoholic peroxide catalyst (more particularly an alkyl peroxide catalyst) which also is heated within the aforementioned temperature range. We prefer to use an alcoholic peroxide catalyst which is normally a liquid ene.

It was known prior to our invention that liquid polymers of chlorotrifluoroethylene could be produced. One method of obtaining such liquid polymers is disclosed in our copending application Serial No. 745,646 filed May 2, 1947, now Patent No. 2,543,530, issued February 27, 1951. The invention claimed in that application is concerned with the pyrolysis of polymeric chlorotrifiuoroethylene, more particularly with the pyrolysis of solid polymers of chlorotrifiuoroethylene, whereby various pyrolysis products are obtained including a substantial amount of monomeric chlorotrifluoroethylene. As also is pointed I out in that application the pyrolysis products include polymers of lower molecular weight than the polymer which was pyrolyzed, which lowmolecular-weight polymers may be obtained in the form of oils, greases, waxes, etc. The process 2 batch-wise polymerization of solutions of the monomer. This method likewise has not been entirely satisfactory. Such batch processes have involved the use of large volumes of solvent, since, in order to obtain a polymer which was sufficiently low in molecular weight, the concentration of monomer in the solvent necessarily had to be limited to about 10%.

The present invention is based on our discovery that stable, high-boiling liquid polymers of chlorotrifluoroethylene can be obtained in. high, overall yields by the catalyzed vapor-phase polymerization of monomeric chlorotrifluoroethylene. The process can be carried out continuously, with obvious advantages, and does not require the use of expensive pressure equipment. It was surprisingly found that not all peroxide catalysts are adapted for catalyzing the vaporphase polymerization of monomeric chlorotrifluoroethylene. More particularly we have found that suitable peroxide catalysts for effecting this vapor-phase polymerization of monomeric chlorotrifluoroethylene are normally liquid alcoholic peroxides, specifically di-(tert.-butyl) peroxide, 2,2-bis(tert.-butylperoxy) butane and mixtures of these peroxides. Acetyl peroxide (an acidic peroxide) was found to be ineifective for the vapor phase polymerization of monomeric chlorotrifluoroethylene. The amount of the catalyst may be varied as desired or as conditions may require, but usually is within the range of from about 0.5% to about 10% by Weight of the monomeric ohlorotrifiuoroethyldescribed in that application is particularly I adapted for use in the conversion of solid poly-v mers of chlorotrifluoroethylene, for example such material in the form of waste scrap, to mono- .meric chlorotrifluoroethylene, but is not especially adapted for use in the production of high yields of liquid polymers of chlorotrifiuoroethylene from solid polymers of this same material.

Another method for the preparation of liquid polymers of chlorotrifluoroethylene involves ene, e. g., from about 1% to about 7% by weight thereof.

In order that those skilled in' the art better may understand how our invention can be carried into effect the following description thereof is given, including the results of a series of tests with different peroxy catalysts, these results being set forth in tabular form for purpose of brevity.

The apparatus employed in carrying out the tests, which will be. described more fully hereafter, included a polymerization tube which was constructed from a 40-inch length of heavywalled Pyrex combustion tubing (25 mm. out

side diameter and 18 mm. inside diameter), to either end of which was sealed a standard taper joint. A thermocouple well, which extended the length of the polymerization tube, was sealed to an adaptor that fitted the input or top end of the tube. This adaptor also was providedwith connections for feeding the catalyst and monomeric chlorotrifiuoroethylene thereto. The poly- 3 4 merization tube arrangedvertically and unpacked, was heated over a 36-inch section by means of Amount an electric furnace which surrounded the tube. Cut Boiling Point, 0. l i Suitable means was provided for controlling the temperature of the main heaters and of. the ring 5 594505 (760 mm) L8 heaters which were attached to the ends of the 43-115 21mm.) III-III II 1.3 Tummlncelculating the time that a given unit ts'dte'oazssistiaaiit???E Tli?? f;?.fi??:::: t? monomeric chlorotrifluoroethylene was mainltitiietelifierii lrt tii iitei itf$229353 10 3 a m Somewhat section of the polymerization tube. viscous liquid. Cryoscoprc determination of The chlorotrifiuoroethylene was fed directly molecular Welght usmg berizerte 1 the solvent into the polymerization tube itsrate being detergave Values of and mdwatmg that mined by passage throu'gli a liouid level flowcompnsed mainly tetraimlar .q i meter For introducing the catalyst to thepolyfiuorpethylene' Llke 011s of 5111.111 oolhng point a s stem was connected to the polymerization tube. y S Iii assembling the apparatus care was taken to 9 z f fl a i i provide for continuous flow of the catalyst and fj' g 1 1 o ggggenia'i 2 g g fcrmegtlonl g c i g gig ig' 2o fluorine at room temperature, for four hours proed e g f o 5 P t a duced little change; some turbidity developed but gi F E s g is i if z' at there was no apparent increase in viscosity. mg 2 12x781 th t m monomeric chl r t f D cstillatiorfi (if the product from run No. 2 gave L :4 r .fluoroethylene was introduced from the opposite Ions as 0 CW5 side. The lower end of the reaction or poly- Amount merization tube was connected through ashort Cut Boiling Point, 0. in condenser to a receiver flask cooled in ice. Dry Grams Ice (solid carbon dioxide) traps were arranged to collect unreacted chlorotrifluoroethylene. i: $1 3,533533 In carrying out the tests the furnace was first 95 d n d k v 100 (20 mm.)-l92 (0.18 mm)... 0.3 brought to temperature, the system was flushed iii i i f i'ff with an. inert gas, specifically nitrogen, and the feed of monomer and of catalyst was thenstarted. 3r To prevent any back diffusion of. gases from. the 0 Per Per Per reaction tube a slow stream (approximately 0.5 AnclysisoiCutB Cent Cent Cent liter per hour) of nitrogen was introduced at the 0 H 01 top of the plunger feed system during the run. The .product which was collected in the receiving 40 (Fmcumcd for (CEFBCDZ 2 :2 3 3 flask was either a yellow or brown liquid. In mm "{23,29 1, 30117 445 determining the percent conversion, the weight of catalyst introduced to the reaction tube during The Hquid product from Run 3 was also the. run was subtracted from the weight of liquid distilled with the following results: material which was collected. The material collected in the dry ice traps comprised mainly unreacted monomeric chlorotrifluoroethylene and, Cut Boiling Point,C. 32 3 probably also, small amounts of low-boiling decomposition products of the catalyst. 43434 (760 mm) 10. 5 The results of a number of different runs are 143 )165 (22mm)..- 10.8 summarized in Table I.

Table I QF GFCIIeed Catalyst Y Aver- 0011- Total Conver- Run age tact Liquid sion 1 Re No. Total Gms. T ClerI T68?! Tgllp 'lime Pgiduct CPert gg er y e on u ec. ms. en g fir. p .F'eed Gms. Cent 89 21. 8 Dl-(t.-butyl) peroxide; 6. 9 6. 1 280 62 22. 8 l8. 8 68. 1 96 83 38.4 d 3. 7 3. 1 .282 35 12.2 11.0 70.8 96 101 404 do 3. 6 3. 6 426' 27 23. 3 l9. 5 77. 1 97 4- 59 39.4. Mixture. of about .4. l 2. 4 2.67 35 9. 4 11.8 46. 6 91 2, 2-bis(t.-b u t y l p e roxy) butane and about 30% of .di-(t-.- bntyl) peroxide. 5 89 '44. 5 Acetyl peroxide l. 4 4. 3 171 '38' 4.1 0 82. 1 93 6- 0..-. 78; '39 .-..-(10 -1.7 4-3 .282; 35 4. 2 0 81.5 104 .1 The cr cent OLCEFCFCI whichwas converted to recoverable liquid product; In dctcrminingthis, the weight oi catalyst ied was en tracted from the weight of liquid product collected inthe receiving flask.

3O'%, solution in dimethyl phihaiate; The Per Cent In Feed is calculated on pure acetyl peroxide.

The products from several runs were distilled 70 Results similar to those described in the table through a 10 cm. column equipped with a spiral withreference to runs 1-4 are obtained when 2,2- wire packing in order to obtain information as bis(tert.-butylperoxy) butane (a liquid at room to the distribution of the various fractions. temperature) alone is used as a catalyst instead The distillation data on the product of run of di-(tert.-butyl) peroxide (also a liquid at No. lare as follows: room temperature) or a mixture of (ii-(tertbutyl) peroxide and 2,2-bis(tert.-buty1peroxy) butane, the formula for which is (IJHB HaC-(i-CHS As is shown by the results of runs 5 and 6 acetyl peroxide (diacetyl peroxide) is not efiective as a catalyst for the vapor-phase polymerization of monomeric chlorotrifiuoroethylene.

Instead of introducing nitrogen to the reaction zone, other gases which are inert during the polymerization reaction may be introduced thereto along with the monomeric chlorotrifluoroethylene and catalyst, for example carbon dioxide, argon, helium, etc. If desired, the polymerization reaction can be efiected in the presence of air or oxygen. In other words, the reaction will proceed satisfactorily in the presence of the small amount of air or oxygen which normally might be present in, or be introduced to, the reaction zone during the polymerization.

The temperature at which the polymerization of the monomer is efiected should be at least 150 C. and not higher than 450 C. If the temperature in the reaction zone is below 150 C., the time required is too long for practical purposes while at temperatures above 450 C., the proportion of polymers of very low molecular weight (mainly dimer and trimer) becomes excessive.

If desired, the polymerization reaction can be eiiected at superatmospheric pressure. e. g., at pressures ranging from slightly above atmospheric such as 1.05 atmospheres to a pressure of 500 atmospheres or even as high as 1000 atmospheres. Since the temperatures of polymerization used in practicing our invention are above the critical temperature of monomeric chlorotrifiuoroethylene, the monomer is in the vapor phase regardless of the particular pressure employed.

ferred temperature range of 200-400 C., the

contact time is usually within the range of 15 or 20 seconds to 1 or 2 minutes.

It will be understood, of course, by those skilled in the art that the recovered monomeric chlorotrifluoroethylene can be re-cycled, as by recirculation through the polymerization zone in a continuous system of operation.

In general, the liquid polymers produced as herein described have viscosities within a lubricating oil range.

The polymers resulting from our process can be after-fluorinated if desired, for instance in the manner disclosed in copending Kropa application Serial No. 622,088, filed October 12, 1945, now Patent No. 2,497,046, issued February 7, 1950.

We claim:

1. The method of producing liquid polymeric chlorotrifiuoroethylene adapted for use as a lubricant which comprises continuously charging to a conduit leading to a heated reaction zone monomeric chlorotrifiuoroethylene and a catalyst selected from the class consisting of di-(tert.-butyl) peroxide, 2,2-bis-(tert.-buty1 peroxy)butane and mixtures thereof, the amount of the said catalyst corresponding to from 0.5 to 10% by weight of the monomeric chlorotrifluoroethylene which is charged to the said conduit, preventing any back diffusion of gases from the said heated reaction zone by simultaneously charging to the said conduit, prior to the point of charging thereto the said monomeric chlorotrifluoroethylene and the said catalyst, a gas which is inert during the reaction, the said catalyst and monomer being heated together in the said zone in the presence of the said inert gas at a temperature within the range of C. to 450 C. for a period sufficiently long to form a substantial amount of polymeric chlorotrifiuoroethylene which is liquid at room temperature and at atmospheric pressure, and isolating the said polymeric chlorotrifiuoroethylene.

2. A method as in claim 1 wherein the monomeric chlorotrifluoroethylene and the catalyst are heated together in the reaction zones in the presence of the inert gas at a temperature within the range of about 200 C. to about 400 C.

3. A method as in claim 1 wherein the catalyst is di-(tert.-buty1) peroxide.

4. A method as in claim 1 wherein the catalyst is 2,2-bis (tert.-buty1peroxy) butane.

5. A method as in claim 1 wherein the catalyst is a mixture of di-(tert.,-butyl) peroxide and 2,2- bis(tert.-buty1peroxy) butane.

6. The method of producing liquid polymeric chlorotrifiuoromethylene adapted for use as a lubricant which comprises continuously charging to a conduit leading to aheated reaction zone monomeric chlorotrifluoroethylene and a catalyst selected from the class consisting of di-(tert.- butyl) peroxide, 2,2-bis(tert.-butyl peroxy) butane and mixtures thereof, the amount of the said catalyst corresponding to from 1 to 7% by weight of the monomeric chlorotrifluoroethylene which is charged to the said conduit, preventing any back diffusion of gases from said heated reaction zone by simultaneously charging to the said conduit, prior to the point of charging thereto the said monomeric chlorotrifluoroethylene and the said catalyst, a gas which is inert during the reaction, the said catalyst and monomer being heated together in the said zone in the presence of the said inert gas at a temperature within the range of about 200 C. to about 400 C. for a period sufficiently long to form a substantial amount of polymeric chlorotrifluoroethylene which is liquid at room temperature and at atmospheric pressure, and isolating the said polymeric chlorotriiiuoroethylene.

7. A method as in claim 6 wherein the inert gas is nitrogen.

JOHN J. PADBURY. EDWARD L. KROPA.

REFERENCES CITED The following references are of record in the file of this patent: V

Number Industrial and Engineering 

1. THE METHOD OF PRODUCING LIQUID POLYMERIC CHLOROTRIFLUOROETHYLENE ADAPTED FOR USE AS A LUBRICANT WHICH COMPRISES CONTINUOUSLY CHARGING TO A CONDUIT LEADING TO A HEATED REACTION ZONE MONOMERIC CHLOROTRIFLUOROETHYLENE AND A CATALYST SELECTED FROMTHE CLASS CONSISTING OF DI-(TER-BUTYL) PEROXIDE, 2,2-BIS-(TERT-BUTYL PEROXY) BUTANE AND MIXTURES THEREOF, THE AMOUNT OF THE SAID CATALYST CORRESPONDING TO FROM 0.5 TO 10% BY WEIGHT OF THE MONOMERIC CHLOROTRIFLUOROETHYLENE WHICH IS CHARGED TO THE SAID CONDUIT, PREVENTING ANY BACK DIFFUSION OF GASES FROM THE SAID HEATED REACTION ZONE BY SIMULTANEOUSLY CHARGING TO THE SAID CONDUIT, PRIOR TO THE POINT OF CHARGING THERETO THE SAID MONOMERIC CHLOROTRIFLUOROETHYLENE AND THE SAID CATALYST, A GAS WHICH IS INERT DURING THE REACTION, THE SAID CATALYST AND MONOMER BEING HEATED TOGETHER IN THE SAID ZONE IN THE PRESENCE OF THE SAID INERT GAS AT A TEMPERATURE WITHIN THE RANGE OF 150* C. TO 450* C. FOR A PERIOD SUFFICIENTLY LONG TO FORM A SUBSTANTIAL AMOUNT OF POLYMERIC CHLOROTRIFLUOROETHYLENE WHICH IS LIQUID AT ROOM TEMPERATURE AND AT ATMOSPHERIC PRESSURE, AND ISOLATING THE SAID POLYMERIC CHLOROTRIFLUORETHYLENE. 